1. Field of the Invention
The present invention relates to an image heating apparatus that implements a heating process on a toner image on a recording member by contacting a roller onto the recording member and more specifically to a configuration thereof for mounting and axially positioning a bearing portion at an end portion of the roller by a retaining ring.
2. Description of the Related Art
An image forming apparatus that forms and transfers a toner image on a recording member is now widely used. The apparatus then conveys the recording member on which the toner image has been transferred to a heating nip portion of an image heating apparatus and fixes the image on the recording member by nipping and heating the recording member at the heating nip portion. Besides such fixing apparatus, the image heating apparatus is practically used also as a gloss treatment apparatus that applies a desirable degree of gloss by heating a semi-fixed or fixed image or as a reheating apparatus that eliminates residual stress by reheating a fixed image.
The image heating apparatus is arranged in general so that the roller formed of metal is heated in advance and the recording member is conveyed to the heating nip portion formed by press-contacting a pressing member to the roller. The roller is rotably supported by bearing portions disposed at both end portions of the roller.
Japanese Patent Application Laid-open No. 2007-57644 discloses a fixing apparatus having a heating nip portion, through which a recording member is nipped, formed by press-contacting a pressure member to a roller. Here, the roller is provided with one T-shaped cutaway and two I-shaped holes disposed in a circumferential direction at an end thereof. Then, an elastically openable retaining ring having three projections is fitted around the roller in a state in which the respective projections are fitted into the cutaway and the holes. That is, the retaining ring is attached to an outer circumferential surface of the roller in the state in which the projections are inserted into the holes. The retaining ring positions a bearing portion at a predetermined position in an axial direction of the roller to prevent the roller from falling out in the axial direction. The bearing portion has a heat insulating member fitted around the roller and a bearing member fitted around the heat insulating member.
Here, it is preferable to form the roller thinly in order to improve heating responsibility. However, if the roller is thinned, the retaining ring described in Japanese Patent Application Laid-open No. 2007-57644 has a problem that the projections of the retaining ring cannot be fully caught by thin edges of holes of the thinned roller.